Organic light-emitting display apparatus and method of manufacturing the same

ABSTRACT

An organic light-emitting display apparatus and a method of manufacturing the same are disclosed. The organic light-emitting display apparatus includes: an active layer formed on a substrate, a gate electrode including: a first gate electrode layer insulated from the active layer and including a semi-transmissive conductive material, a second gate electrode layer formed on the first gate electrode layer configured to protect the first gate electrode layer, a third gate electrode layer formed on the second gate electrode layer and including a transparent conductive material, and a fourth gate electrode layer formed on the third gate electrode layer and including a conductive material, a pixel electrode including: a first electrode layer formed in the same layer level as the first gate electrode layer and including a semi-transmissive conductive material, a second electrode layer formed on the first electrode layer configured to protect the first electrode layer, a third electrode layer formed on the second electrode layer and including a transparent conductive material, and a fourth electrode layer formed on the third electrode layer and including a conductive material, source and drain electrodes insulated from the gate electrode and electrically connected to the active layer and the pixel electrode, an intermediate layer formed on the pixel electrode and including an organic light-emitting layer, and an opposite electrode formed on the intermediate layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2010-0053599, filed on Jun. 7, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

The present disclosure relates to organic light-emitting displayapparatuses and methods of manufacturing the same.

2. Description of the Related Technology

A method of manufacturing a flat display apparatus, such as an organiclight-emitting display apparatus or a liquid crystal display (LCD)apparatus, is performed on a substrate on which a thin film transistor(TFT), a capacitor, and patterns including wirings for connecting theTFT and the capacitor are formed.

Generally, with regard to substrates of organic light-emitting displayapparatuses, in order to form a fine pattern including a TFT and thelike, the fine pattern is transferred on the substrate by using a maskon which a fine pattern is formed. As such, when an opening portion isformed in a pixel electrode while the pattern is transferred by usingthe mask, the pixel electrode may be damaged due to penetration of anetching solution.

In addition, in order to increase the color reproducibility of a flatdisplay apparatus, it a pixel electrode including a plurality of layersis typically formed in order to increase the optical efficiency of thepixel electrode.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

Aspects of the certain embodiments provide organic light-emittingdisplay apparatuses including a pixel electrode having a plurality oflayers for improving its optical efficiency, for preventing a pixelelectrode from being damaged during manufacturing processes, and methodsof manufacturing the same.

One aspect is an organic light-emitting display apparatus including: anactive layer formed on a substrate, a gate electrode including: a firstgate electrode layer insulated from the active layer and including asemi-transmissive conductive material, a second gate electrode layerformed on the first gate electrode layer configured to protect the firstgate electrode layer, a third gate electrode layer formed on the secondgate electrode layer and including a transparent conductive material,and a fourth gate electrode layer formed on the third gate electrodelayer and including a conductive material, a pixel electrode including:a first electrode layer formed in the same layer level as the first gateelectrode layer and including a semi-transmissive conductive material, asecond electrode layer formed on the first electrode layer configured toprotect the first electrode layer, a third electrode layer formed on thesecond electrode layer and including a transparent conductive material,and a fourth electrode layer formed on the third electrode layer andincluding a conductive material, source and drain electrodes insulatedfrom the gate electrode and electrically connected to the active layerand the pixel electrode, an intermediate layer formed on the pixelelectrode and including an organic light-emitting layer, and an oppositeelectrode formed on the intermediate layer.

Another aspect is a method of manufacturing an organic light-emittingdisplay apparatus, the method including: forming an active layer on asubstrate, forming a gate electrode including a first gate electrodelayer insulated from the active layer and including a semi-transmissiveconductive material, a second gate electrode layer formed on the firstgate electrode layer, a third gate electrode layer formed on the secondgate electrode layer and including a transparent conductive material,and a fourth gate electrode layer formed on the third gate electrodelayer and including a conductive material, forming a pixel electrodeincluding a first electrode layer formed on the same layer level as thefirst gate electrode layer and including a semi-transmissive conductivematerial, a second electrode layer formed on the first electrode layer,a third electrode layer formed on the second electrode layer andincluding a transparent conductive material, and a fourth electrodelayer formed on the third electrode layer and including a conductivematerial, forming source and drain electrodes that are insulated fromthe gate electrode and are electrically connected to the active layerand the pixel electrode, forming an intermediate layer formed on thepixel electrode and including an organic light-emitting layer, andforming an opposite electrode formed on the intermediate layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent bydescribing in detail certain embodiments with reference to the attacheddrawings in which:

FIG. 1 is a cross-sectional view of an embodiment of an organiclight-emitting display apparatus;

FIGS. 2 through 8 are cross-sectional views of an embodiment of a methodof manufacturing an organic light-emitting display apparatus; and

FIG. 9 is a cross-sectional view of another embodiment of an organiclight-emitting display apparatus.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Certain embodiments will be illustrated in the drawings and described indetail in the written description. It is to be appreciated that allchanges, equivalents, and substitutes that do not depart from the spiritand technical scope of the described embodiments are encompassed in thepresent disclosure. In the description, certain detailed explanations ofrelated art are omitted when it is deemed that they may unnecessarilyobscure the disclosure.

While such terms as “first,” “second,” etc., may be used to describevarious components, such components must not be limited to the aboveterms. The above terms are used only to distinguish one component fromanother.

The terms used in the present specification are merely used to describeparticular embodiments. An expression used in the singular encompassesthe expression of the plural, unless it has a clearly different meaningin the context. In the present specification, it is to be understoodthat the terms such as “including” or “having,” etc., are intended toindicate the existence of the features, numbers, steps, actions,components, parts, or combinations thereof disclosed in thespecification, and are not intended to preclude the possibility that oneor more other features, numbers, steps, actions, components, parts, orcombinations thereof may exist or may be added.

Certain embodiments will now be described more fully with reference tothe accompanying drawings.

FIG. 1 is a cross-sectional view of an embodiment of an organiclight-emitting display apparatus 100.

The organic light-emitting display apparatus 100 includes a substrate101, an active layer 103, a gate electrode 110, a pixel electrode 115,source/drain electrodes 132, an intermediate layer 134, and an oppositeelectrode 135.

In some embodiments, the substrate 101 may be formed of transparentglass containing SiO₂. In other embodiments, the substrate 101 may beformed of a transparent plastic material such as an insulating organicmaterial selected from the group consisting of polyethersulphone (PES),polyacrylate (PAR), polyetherimide (PEI), polyethyelene napthalate(PEN), polyethyelene terephthalate (PET), polyphenylene sulfide (PPS),polyallylate, polyimide, polycarbonate (PC), triacetate cellulose (TAC),and cellulose acetate propionate (CAP).

In bottom emission embodiments of the organic light-emitting displayapparatus, in which an image is realized toward the substrate 101, thesubstrate 101 may be formed of a transparent material. In top emissionembodiments of the organic light-emitting display apparatus, in which animage is realized away from the substrate 101, the substrate 101 may maybe formed of a metal. In embodiments where the substrate 101 is formedof a metal, the substrate 101 may include at least one material selectedfrom the group consisting of carbon (C), iron (Fe), chromium (Cr),manganese (Mg), nickel (Ni), titanium (Ti), molybdenum (Mo), stainlesssteel (SUS), Invar alloys, Inconel alloys, Kovar alloys, and the like.In other embodiments, the substrate 101 may be formed of a metal foil.

In order to form a planarized surface on the substrate 101 and toprevent impurity elements from penetrating into the substrate 101, abuffer layer 102 may be formed on the substrate 101. In someembodiments, the buffer layer 102 may be formed of SiO₂ and/or SiN_(X).The buffer layer 102 may be formed by using a deposition method such asa plasma enhanced chemical vapor deposition (PECVD) method, anatmospheric pressure chemical vapor deposition (APCVD) method, or alow-pressure chemical vapor deposition (LPCVD) method, and the like.

The active layer 103, having a predetermined pattern, is formed on thebuffer layer 102. In some embodiments, the active layer 103 may beformed of an inorganic semiconductor, such as amorphous silicon orpolysilicon. In other embodiments, the active layer 103 may be formed ofan organic semiconductor. The active layer 103 includes a source region,a drain region, and a channel region. The source and drain regions maybe formed by doping the active layer 103 with impurities. Doping thesource and drain regions with a Group-III element such as Boron (B), mayform a p-type semiconductor. Doping the source and drain regions with aGroup-V element, such as nitrogen (N), may form an n-type semiconductor.

A capacitor lower electrode 104 may be formed on the buffer layer 102,separate from the active layer 103. In some embodiments, the capacitorlower electrode 104 may be formed of an inorganic semiconductor, such asamorphous silicon or polysilicon. In other embodiments, the capacitorlower electrode 104 may be formed of an organic semiconductor.

A gate insulation layer 105 is formed on the buffer layer 102 and coversthe active layer 103 and the capacitor lower electrode 104. The gateinsulation layer 105 insulates the active layer 103 and the gateelectrode 110 from each other. The gate insulation layer 105 may beformed of an inorganic material, such as SiN_(x) and SiO₂, by using aPECVD method, an APCVD method, a LPCVD method, or the like.

The gate electrode 110 is formed on the gate insulation layer 105. Thegate electrode 110 may include first through fourth gate electrodelayers 106, 107, 108 and 109. The gate electrode 110 may include a firstgate electrode layer 106 including a semi-transmissive conductivematerial, a second gate electrode layer 107 formed on the first gateelectrode layer 106 and protecting the first gate electrode layer 106, athird gate electrode layer 108 formed on the second gate electrode layer107 and including a transparent conductive material, and a fourth gateelectrode layer 109 formed on the third gate electrode layer 108 andincluding a conductive material.

The first gate electrode layer 106 may include at least one of analuminum (Al) alloy, Ti, Mo, MoW, and Ag. The first gate electrode layer106 may be formed on the gate insulation layer 105 by using a sputteringmethod, or the like.

The second gate electrode layer 107 may be formed on the first gateelectrode layer 106, and may include Al, or an oxide formed by oxidizingthe first gate electrode layer 106 with heat or plasma. In someembodiments, the second gate electrode layer 107 may include at leastone of an Al oxide, an oxide of Al alloy, a Ti oxide, a Mo oxide, a MoWoxide, and an Ag oxide.

The third gate electrode layer 108 may be formed on the second gateelectrode layer 107, and may include at least one of ITO, IZO, a Znoxide, GZO, GIZO, GaZO, ZnO, and In₂O₃.

The fourth gate electrode layer 109 may include at least one of silver(Ag), magnesium (Mg), aluminium (Al), platinum (Pt), palladium (Pd),gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr),lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten(W), MoW, and aluminium/copper (Al/Cu). The fourth gate electrode layer109 may include a plurality of layers. In some embodiments, the fourthgate electrode layer 109 may include a first layer formed of MoW, asecond layer formed on the first layer and formed of Al, and a thirdlayer formed on the second layer and formed of Mo.

The pixel electrode 115 may be formed on the same layer level as thegate electrode 110. The pixel electrode 115 may be formed of the samematerial as the gate electrode 110, and may have the same structure asthe gate electrode 110. The pixel electrode 115 may include firstthrough fourth electrode layers 111, 112, 113, and 114. The pixelelectrode 115 may include a first electrode layer 111 including asemi-transmissive conductive material, a second electrode layer 112formed on the first electrode layer 111 and protecting the firstelectrode layer 111, a third electrode layer 113 formed on the secondelectrode layer 112 and including a transparent conductive material, anda fourth electrode layer 114 formed on the third electrode layer 113 andincluding a conductive material.

The first electrode layer 111 may include at least one of an Al alloy,Ti, Mo, MoW, and Ag. In some embodiments, the Al alloy may include Aland at least one of Si, Ni, La, Ge and Co. The first electrode layer 111may be formed on the gate insulation layer 105 by using a sputteringmethod, or the like. The first electrode layer 111 may function as ametal mirror that partially transmits light and partially reflectslight. The first electrode layer 111 may be used as a semi-transmissivemirror of an organic light-emitting display apparatus having a lightresonance structure.

The second electrode layer 112 may be formed on the first electrodelayer 111. The second electrode layer 112 may include Al, or an oxideformed by oxidizing the first electrode layer 111 with heat or plasma.In embodiments where the second electrode layer 112 includes an oxide,the second electrode layer 112 may include at least one selected of anAl oxide such as Al₂O₃, an oxide of an Al alloy, a Ti oxide, a Mo oxide,a MoW oxide, and an Ag oxide. The second electrode layer 112 preventsthe first electrode layer 111 from corroding through a pin hole of thethird electrode layer 113. The fourth electrode layer 114 may be etchedto expose the third electrode layer 113. The second electrode layer 112prevents a reduction in a hole injection efficiency due to the firstelectrode layer 111 having semi-transmissive characteristics. The secondelectrode layer 112 prevents a reduction in the optical efficiency ofthe organic light-emitting display apparatus 100 due to the firstelectrode layer 111. In some embodiments, the second electrode layer 112may include an oxide-containing material.

The third electrode layer 113 may be formed on the second electrodelayer 112, and may include at least one of ITO, IZO, ZnO, GZO, GIZO,GaZO, a Zn oxide and In₂O₃. In some embodiments, with the thirdelectrode layer 113 formed of ITO, a heat treatment process may be used.In such embodiments, while crystallizing ITO, the size and number of pinholes formed in the ITO may increase.

The fourth electrode layer 114 may include at least one of Ag, Mg, Al,Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, MoW, and Al/Cu. A portionof the fourth electrode layer 114 may be removed to form a first openingportion 114 a so as to expose the third electrode layer 113 through thefirst opening portion 114 a. The intermediate layer 134 contacts thethird electrode layer 113 of the pixel electrode 115 through the firstopening portion 114 a.

A capacitor upper electrode 120 may be formed on the gate insulationlayer 105 so as to face the capacitor lower electrode 104. The capacitorupper electrode 120 may be formed of the same material as the gateelectrode 110 and the pixel electrode 115. The capacitor upper electrode120 may have the same structure as the gate electrode 110 and the pixelelectrode 115. The capacitor upper electrode 120 may include firstthrough fourth capacitor electrode layers 116, 117, 118 and 119. Thecapacitor upper electrode 120 may include a first capacitor electrodelayer 116 including a semi-transmissive conductive material, a secondcapacitor electrode layer 117 formed on the first capacitor electrodelayer 116 and protecting the first capacitor electrode layer 116, athird capacitor electrode layer 118 formed on the second capacitorelectrode layer 117 and including a transparent conductive material, anda fourth capacitor electrode layer 119 formed on the third capacitorelectrode layer 118 and including a conductive material. The firstthrough fourth capacitor electrode layers have been described in detailwith the detailed descriptions of the gate electrode 110 and the pixelelectrode 115, and thus their detailed description will not be repeated.

The capacitor lower electrode 104 and the capacitor upper electrode 120,which are respectively formed on and below the gate insulation layer 105to form one capacitor, are formed in the same layer level, like theactive layer 103 and the gate electrode 110. Accordingly, the thicknessof the organic light-emitting display apparatus 100 may be efficientlyreduced.

A planarization layer 131 may be formed on the gate insulating layer 105and may cover the gate electrode 110, the pixel electrode 115, and thecapacitor upper electrode 120. The planarization layer 131 may be formedof various insulation materials. In some embodiments, the planarizationlayer 131 may be formed of an inorganic material, such as an oxide or anitride. In other embodiments the planarization layer 131 may be formedof an organic material.

Some examples of inorganic insulation layer materials for forming theplanarization layer 131 include SiO₂, SiN_(x), SiON, Al₂O₃, TiO₂, Ta₂O₅,HfO₂, ZrO₂, BST, and PZT. Some examples of organic insulation layermaterials for forming the planarization layer 131 include a general-usepolymer (PMMA, PS), a polymer derivative having a phenol group, anacrylic polymer, an amide-based polymer, an aryl ether-based polymer, anamide-based polymer, a fluorine polymer, a p-xylene-based polymer, avinyl alcohol-based polymer, and a blend of these. The planarizationlayer 131 may be formed of a composite stack of an inorganic insulationlayer and an organic insulation layer. The planarization layer 131 maybe formed by using a spin coating method or the like.

The planarization layer 131 may include a second opening portion 131 aabove the first opening portion 114 a.

The planarization layer 131 may include a contact hole exposing thesource/drain regions of the active layer 103. The source/drainelectrodes 132 may be formed to respectively contact the source/drainregions of the active layer 103 via the contact hole. The source/drainelectrodes 132 are connected to the fourth electrode layer 114 of thepixel electrode 115.

In some embodiments, the source/drain electrodes 132 may have amulti-layered structure.

A pixel defining layer 133 may be formed on the planarization layer 131and may cover the source/drain electrodes 132. The pixel defining layer133 may include a third opening portion 133 a that exposes the thirdelectrode layer 113 of the pixel electrode 115. The third openingportion 133 a may be formed to contact the first opening portion 114 aor may be formed in the first opening portion 114 a. In someembodiments, the pixel defining layer 133 may be formed of an organicmaterial. In other embodiments, the pixel defining layer 133 may beformed of an inorganic material.

The intermediate layer 134 may be formed in the third opening portion133 a to contact the third electrode layer 113 of the pixel electrode115. The intermediate layer 134 may include an organic light-emittinglayer.

The intermediate layer 134 may emit light by electrical driving of thepixel electrode 115 and the opposite electrode 135.

The intermediate layer 134 may be formed of an organic material. Inembodiments where the organic light-emitting layer included in theintermediate layer 134 is formed of a low-molecular weight organicmaterial, a hole injection layer (HIL) and a hole transport layer (HTL)may be disposed between the organic light-emitting layer and the pixelelectrode 115, and an electron transport layer (ETL) and an electroninjection layer (EIL) may be disposed between the organic light-emittinglayer and the opposite electrode 135. Other layers may also be stacked.Examples of the organic material for forming the intermediate layer 134include copper phthalocyanine (CuPc),N,N′-Di(naphthalene-l-yl)-N,N′-diphenyl-benzidine (NPB),tris-8-hydroxyquinoline aluminum (Alq3), and the like.

In embodiments where the organic light-emitting layer is formed of apolymer organic material, the intermediate layer 134 may include only anHTL that is disposed between the organic light-emitting layer and thepixel electrode 115. The HTL may be formed of, for example,poly(2,4-ethylenedioxythiophene) (PEDOT) or polyaniline, and may beformed on the pixel electrode 115 by using an inkjet printing method, aspin coating method, or the like. The polymer organic light-emittinglayer may be formed of PPV, soluble PPV's, cyano-PPV, polyfluorene, etc.and a color pattern may be formed in the organic light-emitting layer byusing an inkjet printing method, a spin coating method, a thermaltransfer method using a laser, or the like.

The opposite electrode 135 may be formed on the intermediate layer 134.The opposite electrode 135 may be formed by depositing a metal having alow work function, such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li,Ca, and a compound of these, or the like, and depositing a transparentconductive material, such as ITO, IZO, ZnO, or In₂O₃, or the likethereon.

A sealing member (not shown) may be formed on the opposite electrode135. The sealing member may be formed to protect the intermediate layer134 and/or other layers from water or oxygen from the outside, and maybe formed of a transparent material. In some embodiments, the sealingmember may be formed of glass, plastic, or a multi-layer structure oforganic and inorganic materials.

FIGS. 2 through 8 are cross-sectional views illustrating an embodimentof a method of manufacturing the organic light-emitting displayapparatus 100 of FIG. 1.

The method will be described sequentially in manufacturing order withreference to FIGS. 2 through 8.

First, referring to FIG. 2, the buffer layer 102 is formed on thesubstrate 101, and the active layer 103 and the capacitor lowerelectrode 104 are formed on the buffer layer 102. The active layer 103and the capacitor lower electrode 104 each have a predetermined patternand are separated from each other. In some embodiments, the active layer103 and the capacitor lower electrode 104 may be formed at the same timeby using a photolithography method using one mask.

Referring to FIG. 3, the gate insulation layer 105 is formed on thesubstrate 101, and covers the active layer 103 and the capacitor lowerelectrode 104, and the gate electrode 110, the pixel electrode 115, andthe capacitor upper electrode 120 are formed on the gate insulationlayer 105. In some embodiments, the gate electrode 110, the pixelelectrode 115, and the capacitor upper electrode 120 may be formed bystacking the same materials and using a photolithography method usingone mask.

In the embodiment shown, the gate electrode 110, the pixel electrode115, and the capacitor upper electrode 120 each include four layers. Thefour layers may be stacked, and the first layers (first gate electrodelayer 106, first electrode layer 111 and first capacitor electrode layer116) may include Ag, the second layers (second gate electrode layer 107,second electrode layer 112 and second capacitor electrode layer 117) mayinclude Al₂O₃, the third layers (third gate electrode layer 108, thirdelectrode layer 113 and third capacitor electrode layer 118) may includeITO, and the fourth layers (fourth gate electrode layer 109, fourthelectrode layer 114 and fourth capacitor electrode layer 119) mayinclude MoW, Al and Mo. The four layers may be formed with predeterminedpatterns by using a photolithography method to form the gate electrode110, the pixel electrode 115, and the capacitor upper electrode 120.

In the embodiment shown, the second electrode layer 112 of the pixelelectrode 115 may include an oxide formed by oxidizing the firstelectrode layer 111 with heat or plasma. When the second electrode layer112 includes the oxide, the thickness of the second electrode layer 112may be 3% or less of the thickness of the first electrode layer 111.When the ITO used to form the third electrode layer 113 of the pixelelectrode 115 is crystallized during a heat treatment process, the sizeand number of pin holes formed in the ITO may be increased. The presenceof the second electrode layer 112 prevents an etching solution frompenetrating into a lower electrode layer through a pin hole of the thirdelectrode layer 113, and thereby prevents damage the lower electrodelayer in a subsequent process of forming the first opening portion 114a, when the portion of the fourth electrode layer 114 is removed toexpose the third electrode layer 113 through the first opening portion114 a. Referring to FIG. 4, the planarization layer 131 is formed of aninsulation material on the gate insulation layer 105, and covers thegate electrode 110, the pixel electrode 115, and the capacitor upperelectrode 120. A contact hole is formed in the planarization layer 131.Source and drain regions of the active layer 103 may be exposed throughthe contact hole. To form the contact hole, a photolithography methodmay be used. The second opening portion 131 a may be formed in theplanarization layer 131. The fourth electrode layer 114 of the pixelelectrode 115 is exposed through the second opening portion 131 a. Ahole that exposes the fourth electrode layer 114 of the pixel electrode115 may further be formed in the planarization layer 131 so as toconnect the pixel electrode 115 and a source/drain electrode to beformed later.

Referring to FIG. 5, the source/drain electrodes 132 are formed. Thesource/drain electrodes 132 contact the source and drain regions of theactive layer 103, respectively. The source/drain electrodes 132 alsocontact the fourth electrode layer 114 of the pixel electrode 115. Thesource/drain electrodes 132 may be formed of a multi-layer structureincluding various conductive layers.

Referring to FIG. 6, the first opening portion 114 a is formed in thefourth electrode layer 114 of the pixel electrode 115. The first openingportion 114 a may be formed by etching the fourth electrode layer 114that is exposed through the second opening portion 131 a formed in theplanarization layer 131. The first opening portion 114 a is formed tocorrespond to the second opening portion 131 a.

The fourth electrode layer 114 of the pixel electrode 115 may be etchedby using a wet etching process. In some embodiments, an etching solutionmay include at least one of a phosphoric acid solution, a nitric acidsolution, an acetic acid solution and the like. In embodiments where thefourth electrode layer 114 has a multi-layered structure including afirst electrode layer including MoW, a second layer formed on the firstelectrode layer and including Al, and a third layer formed on the secondlayer and including Mo, the etching solution may be a mixed acidincluding a phosphoric acid solution, a nitric acid solution, an aceticacid solution or the like. In some embodiments, an amount of thephosphoric acid may be about 70% or less of the entire amount of theetching solution.

The second electrode layer 112 formed on the first electrode layer 111and including Al or a metal oxide may prevent the first electrode layer111 from being damaged during processes. Without the second electrodelayer 112, while the fourth electrode layer 114 is etched to form thefirst opening portion 114 a, an etching solution may penetrate into alower electrode layer through a pin hole of the third electrode layer113. The first electrode layer 111 may thus be corroded and damaged dueto the etching solution. When the first electrode layer 111 is damaged,a light resonance structure may not be obtained by transmitting andreflecting light.

Referring to FIG. 7, the pixel defining layer 133 is formed on theplanarization layer 131, and covers the source/drain electrodes 132. Thepixel defining layer 133 may be formed of an organic material. The thirdopening portion 133 a may be formed in the pixel defining layer 133 tocontact the first opening portion 114 a or in the first opening portion114 a. The third electrode layer 113 of the pixel electrode 115 isexposed through the third opening portion 133 a.

Referring to FIG. 8, the intermediate layer 134 and the oppositeelectrode 135 are sequentially formed in the order stated on the thirdelectrode layer 113 of the pixel electrode 115, which is exposed throughthe third opening portion 133 a of the pixel defining layer 133, and onthe pixel defining layer 133. The intermediate layer 134 includes anorganic light-emitting layer. Materials for forming the intermediatelayer 134 and the opposite electrode 135 are the same as described aboveand thus descriptions thereof will be omitted.

Although not shown in FIG. 8, a sealing member may be disposed on theopposite electrode 135 to face a surface of the substrate 101. Thesealing member may be formed to protect the intermediate layer 134 fromwater or oxygen from the outside, and may be formed of a transparentmaterial. In some embodiments, the sealing member may be formed ofglass, plastic, or a multi-layer structure of organic and inorganicmaterials.

FIG. 9 is a cross-sectional view of another embodiment of an organiclight-emitting display apparatus 100. The embodiment of organiclight-emitting display apparatus 100 of FIG. 9 includes a barrier layer111 a, formed below the first electrode layer 111 of the pixel electrode115. The embodiment also includes a gate barrier layer 106 a, formedbelow the first gate electrode layer 106 of the gate electrode 110, anda capacitor barrier layer 116 a formed below the first capacitorelectrode layer 116 of the capacitor upper electrode 120. Other elementshave the same or similar functions as in the above-describedembodiments, and thus their detailed descriptions will not be repeated.The pixel electrode 115 will be described in detail. Since the gateelectrode 110 and the capacitor upper electrode 120 are formed of thesame material in the same layer level as the pixel electrode 115, andhave the same structure as the pixel electrode 115, their detaileddescriptions will not be repeated.

Referring to FIG. 9, the pixel electrode 115 includes the barrier layer111 a formed on the gate insulation layer 105, the first electrode layer111 formed on the barrier layer 111 a and including a semi-transmissiveconductive material, the second electrode layer 112 formed on the firstelectrode layer 111 and protecting the first electrode layer 111, thethird electrode layer 113 formed on the second electrode layer 112 andincluding a transparent conductive material, and the fourth electrodelayer 114 formed on the third electrode layer 113 and including aconductive material.

The barrier layer 111 a may be formed below the first electrode layer111, and may include at least one of ITO, IZO, a Zn oxide, GZO, GIZO,GaZO, ZnO and In₂O₃. By forming the barrier layer 111 a, an adhesiveforce between the first electrode layer 111 and the gate insulationlayer 105 may be increased. Consequently, during a patterning operation,an etching solution and moisture may be prevented from penetrating intothe organic light-emitting display apparatus 100, thereby improving thereliability of the organic light-emitting display apparatus 100.

In some embodiments, the gate electrode 110 and the pixel electrode 115may be formed of the same material in the same layer level, therebyreducing the number of processes. In addition, the capacitor lowerelectrode 104 and the active layer 103 may be formed of the samematerial in the same layer level at the same time, and the capacitorupper electrode 120 and the gate electrode 110 may be formed at the sametime, thereby further reducing the number of processes.

In some embodiments, by forming the pixel electrode 115 to have astacked structure including four layers, where the second electrodelayer 112 protects the first electrode layer 111, a surface of the firstelectrode layer 111 may be prevented from being damaged in a subsequentprocess. In addition, since the second electrode layer 112 includes anoxide, a reduction in the optical efficiency of the organiclight-emitting display apparatus 100, due to the first electrode layer111 as a semi-transmissive conductive layer, may be prevented.

In some embodiments, the flat display apparatus may include an organiclight-emitting display apparatus. In other embodiments, various displayapparatuses may include a liquid crystal display (LCD) apparatus or thelike.

In the described embodiments, a single thin film transistor and a singlecapacitor are illustrated for convenience of illustration. In otherembodiments, the organic light-emitting display apparatus may include aplurality of thin film transistors and a plurality of capacitors.

In some embodiments, since the organic light-emitting display apparatusmay be manufactured by using a small number of masks, costs may bereduced due to a reduction in the number of masks and simplification ofprocesses.

In some embodiments, a pixel electrode has a multi-layered structureincluding a second electrode layer, and the second electrode layer mayprevent a first electrode layer from being damaged through a hole formedin a third electrode layer when a fourth electrode layer of the pixelelectrode is etched. In addition, the pixel electrode may include asecond electrode layer, and thus a reduction in the optical efficiencyof the organic light-emitting display apparatus due to the firstelectrode layer as a semi-transmissive conductive layer may beprevented.

While certain embodiments have been particularly shown and described, itwill be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope of the present invention as defined by thefollowing claims.

1. An organic light-emitting display apparatus comprising: an activelayer formed on a substrate; a gate electrode comprising: a first gateelectrode layer insulated from the active layer and comprising asemi-transmissive conductive material, a second gate electrode layerformed on the first gate electrode layer configured to protect the firstgate electrode layer, a third gate electrode layer formed on the secondgate electrode layer and comprising a transparent conductive material,and fourth gate electrode layer formed on the third gate electrode layerand comprising a conductive material; a pixel electrode comprising: afirst electrode layer formed in the same layer level as the first gateelectrode layer and comprising a semi-transmissive conductive material,a second electrode layer formed on the first electrode layer configuredto protect the first electrode layer, third electrode layer formed onthe second electrode layer and comprising a transparent conductivematerial, and a fourth electrode layer formed on the third electrodelayer and comprising a conductive material; source and drain electrodesinsulated from the gate electrode and electrically connected to theactive layer and the pixel electrode; an intermediate layer formed onthe pixel electrode and comprising an organic light-emitting layer; andan opposite electrode formed on the intermediate layer.
 2. The organiclight-emitting display apparatus of claim 1, wherein each of the firstgate electrode layer and the first electrode layer comprises at leastone of an aluminum (Al) alloy, titanium (Ti), molybdenum (Mo), MoW, andsilver (Ag).
 3. The organic light-emitting display apparatus of claim 1,wherein each of the second gate electrode layer and the second electrodelayer comprises at least one of Al, an Al oxide, an oxide of an Alalloy, a Ti oxide, a Mo oxide, a MoW oxide, and an Ag oxide.
 4. Theorganic light-emitting display apparatus of claim 1, wherein each of thethird gate electrode layer and the third electrode layer comprises atleast one of ITO, IZO, ZnO, GZO, GIZO, GaZO, a Zn oxide and In₂O₃. 5.The organic light-emitting display apparatus of claim 1, wherein each ofthe fourth gate electrode layer and the fourth electrode layer comprisesat least one of silver (Ag), magnesium (Mg), aluminium (Al), platinum(Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium(Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo),titanium (Ti), tungsten (W), MoW, and aluminium/copper (Al/Cu).
 6. Theorganic light-emitting display apparatus of claim 1, wherein the pixelelectrode further comprises: a barrier layer formed below the firstelectrode layer of the pixel electrode, wherein the barrier layercomprises at least one of ITO, IZO, ZnO, GZO, GIZO, GaZO, a Zn oxide andIn₂O₃.
 7. The organic light-emitting display apparatus of claim 1,wherein the fourth electrode layer comprises an opening configured toexpose the third electrode layer formed below the fourth electrodelayer.
 8. The organic light-emitting display apparatus of claim 1,wherein the intermediate layer contacts the third electrode layer of thepixel electrode.
 9. The organic light-emitting display apparatus ofclaim 1, further comprising: a capacitor lower electrode layer formed onthe same layer level as the active layer, and spaced apart from theactive layer; and a capacitor upper electrode layer comprising: a firstcapacitor electrode layer insulated from the capacitor lower electrodelayer, and formed on the same layer level as the pixel electrode,wherein the first capacitor electrode layer corresponds to the firstelectrode layer, and wherein the first capacitor electrode layercomprises a semi-transmissive conductive material, a second capacitorelectrode layer formed on the first capacitor electrode layer andcomprising at least one of an oxide or Al, a third capacitor electrodelayer formed on the second capacitor electrode layer and comprising atransparent conductive material, and a fourth capacitor electrode layerformed on the third capacitor electrode layer and comprising aconductive material.
 10. A method of manufacturing an organiclight-emitting display apparatus according to claim 1, the methodcomprising: forming the active layer on the substrate; forming the gateelectrode; forming the pixel electrode; forming the source and drainelectrodes; forming the intermediate layer on the pixel electrode; andforming the opposite electrode on the intermediate layer.
 11. The methodof claim 10, wherein each of the first gate electrode layer and thefirst electrode layer comprises at least one of an aluminum (Al) alloy,titanium (Ti), molybdenum (Mo), MoW, and silver (Ag).
 12. The method ofclaim 10, wherein each of the second gate electrode layer and the secondelectrode layer comprises Al, or at least one of an Al oxide, an oxideof an Al alloy, a Ti oxide, a Mo oxide, a MoW oxide, and a Ag oxide, andwherein the second gate electrode layer and the second electrode layerare respectively formed by oxidizing each of the first gate electrodelayer and the first electrode layer with heat or plasma.
 13. The methodof claim 10, wherein each of the third gate electrode layer and thethird electrode layer comprises at least one of ITO, IZO, ZnO, GZO,GIZO, GaZO, a Zn oxide, and In₂O₃.
 14. The method of claim 10, whereineach of the fourth gate electrode layer and the fourth electrode layercomprises at least one of silver (Ag), magnesium (Mg), aluminium (Al),platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd),iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum(Mo), titanium (Ti), tungsten (W), MoW, and aluminium/copper (Al/Cu).15. The method of claim 10, further comprising: forming a barrier layerformed below the first electrode layer of the pixel electrode, whereinthe barrier layer comprises at least one of ITO, IZO, ZnO, GZO, GIZO,GaZO, a Zn oxide, and In₂O₃.
 16. The method of claim 10, wherein thegate electrode and the pixel electrode are formed at the same time. 17.The method of claim 10, further comprising: forming an opening portionin the fourth electrode layer so as to expose the third electrode layer.18. The method of claim 10, further comprising: forming a capacitorlower electrode layer on the same layer level as the active layer, andspaced apart from the active layer; and forming a capacitor upperelectrode layer, which comprises: a first capacitor electrode layerinsulated from the capacitor lower electrode layer, on the same layerlevel as the pixel electrode and corresponding to the first electrodelayer, and comprising a semi-transmissive conductive material, a secondcapacitor electrode layer on the first capacitor electrode layer andcomprising an oxide or Al, a third capacitor electrode layer on thesecond capacitor electrode layer and comprising a transparent conductivematerial, and fourth capacitor electrode layer on the third capacitorelectrode layer and comprising a conductive material.